Could Tack-Curing Influence Margin Continuity and Conversion Degree of a Universal Dual-Curing Cement?

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• The long-term success of full-ceramic crowns relies heavily on proper polymerization of dental cements.
• Understanding the impact of different polymerization techniques on cement properties is essential for clinical application.

Purpose of the Study:

• To evaluate the effect of two distinct polymerization protocols on the marginal adaptation and degree of conversion (DC) of a universal dual-curing cement.
• To assess the influence of thermal aging on these properties.

Main Methods:

• Full-ceramic crowns (reinforced lithium silicate) were fabricated and cemented using a universal dual-curing cement.
• Two polymerization protocols were tested: G1 (microbrush excess removal, 1 min waiting, 20s light cure) and G2 (5s tack cure, scaler excess removal, 20s light cure).
• Marginal adaptation was analyzed using micro-computed tomography, and DC was measured via Raman spectroscopy before and after 10,000 thermal cycles.

Main Results:

• The tack-curing protocol (G2) resulted in significantly poorer marginal adaptation compared to the standard protocol (G1).
• No significant differences in marginal adaptation were observed between groups after thermal aging.
• Baseline DC was high across all samples, with no initial protocol-dependent variations. Thermal aging increased DC in the G1 group.

Conclusions:

• The selection of an appropriate polymerization protocol is critical for achieving optimal marginal adaptation in full-ceramic restorations.
• While both protocols yielded high initial DC, the standard protocol demonstrated superior marginal integrity, which was maintained after aging.
• Clinical recommendations should favor protocols ensuring better marginal seal to enhance restoration durability.